1. Field of the Invention
Aspects of the present invention relate to an image reading apparatus and image forming apparatus including the same, and more particularly, to an image reading apparatus including a plurality of image sensors for a double-side reading (i.e., reading images of both sides of a document sheet at a time), and an image forming apparatus including the same.
2. Description of the Related Art
In general, an image reading apparatus has a function of reading an image of a document to convert it into computer readable image data. Such image reading apparatuses can be divided into two types: a flatbed type, which includes an image reading platform for accommodating a document and an image sensor that moves reciprocatingly along the image reading platform to read an image of the document; and an automatic document feeding type, which reads an image of the document by making the document move past a stationary image sensor.
As described in Japanese Patent Laid-Open Publication No. 2004-187144 (publication date: Jul. 2, 2004) entitled “IMAGE READING APPARATUS,” an image reading apparatus in combination with the flatbed and automatic document feeding types has been recently developed. FIG. 1 shows the combination-type image reading apparatus disclosed in the aforementioned patent laid-open publication.
As shown in FIG. 1, an image reading apparatus 100 includes an image reading platform 110 having an image sensor part 111 and a light exposing part 112 therein, and an automatic document feeder 120 provided at an upper side portion of the image reading platform 110.
The light exposing part 112 is configured to be reciprocated right and left in the image reading platform 110 to irradiate light on a document 1 placed on the image reading platform 110. A reflected light from the document 1 is transmitted to the image sensor part 111 which produces data using the reflected light.
Further, the automatic document feeder 120 includes a paper-feeding part 121, a first reading part 122, a second reading part 123 and a paper discharge part 125. After being supplied to the paper-feeding part 121, a document is initially moved past the first reading part 122 while one side of the document is read through the light exposing part 112 and the image sensor part 111 positioned below the document, then is moved past the second reading part 123 while the other side of the document is read by an image sensor part 124, and finally is discharged through the paper discharge part 125.
The image sensor part 124 installed at the second reading part 123 is usually provided with a contact image sensor. In such a case, the document is moved past the second reading part 123 while its surface makes contact with the contact image sensor.
However, in a case where the reading of the document is performed using an automatic document feeder 120, the document is always moved with its surface making contact with the image sensor part 124 of the second reading part 123, even when double-side printing is not performed. This unnecessary contact between the image sensor part 124 and the document creates a problem in that the quality of data produced by reading the document is degraded as the image sensor part 124 is damaged or foreign matters are attached to the image sensor part 124.
Further, as shown in FIG. 1, in a case where the contact image sensor is used as the image sensor part 124, the image sensor part 124 is installed so that the distance between the image sensor part 123 and the side of the document being read by the image sensor part 124 decreases in order to read the image of the document correctly, which causes a problem because the transferring speed of the document is substantially lowered.
Accordingly, this leads to a reduction of the document reading speed when a one-side reading is performed using the automatic document feeder 120, since the document is moved past the second reading part 123 at a lowered transferring speed.